Determine #defined string length at compile time

Question

I have a C-program (an Apache module, i.e. the program runs often), which is going to write() a 0-terminated string over a socket, so I need to know its length.

The string is #defined as:

#define POLICY "<?xml version=\"1.0\"?>\n" \    "<!DOCTYPE cross-domain-policy SYSTEM\n" \    "\"http://www.adobe.com/xml/dtds/cross-domain-policy.dtd\">\n" \    "<cross-domain-policy>\n" \    "<allow-access-from domain=\"*\" to-ports=\"8080\"/>\n" \    "</cross-domain-policy>\0" 

Is there please a way, better than using strlen(POLICY)+1 at the runtime (and thus calculating the length again and again)?

A preprocessor directive, which would allow setting POLICY_LENGTH already at compile time?

Answer 1

Use sizeof(). e.g. sizeof("blah") will evaluate to 5 at compile-time (5, not 4, because the string literal always includes an implicit null-termination character).